This invention relates to coaxial transmission lines constructed by machining channels within an electrically conducting plate and, more particularly, to an adapter permitting the connection of either a coaxial transmission line or a waveguide with a mode launcher to a port in the plane of the plate.
Cross-reference is hereby made to three copending applications pertaining to microwave systems assigned to the same assignee; "Square Conductor Coaxial Coupler" invented by T. Hudspeth, R. V. Basil and H. H. Keeling, Ser. No. 468,826, filed on Feb. 23, 1983, "Coaxial Transmission Line Crossing" invented by T. Hudspeth and H. H. Keeling, Ser. No. 468,827, filed on Feb. 23, 1983, and "Ferrite Modulator Assembly For Beacon Tracking System" invented by T. Hudspeth, H. S. Rosen and F. Steinberg, Ser. No. 469,870, filed on Feb. 25, 1983. These applications are hereby incorporated by reference in their entirety.
Coaxial transmission lines fine wide use in microwave circuitry as they support a TEM (transverse electromagnetic) wave for the communication of the microwave energy over a wide bandwidth. A particular use of the coaxial transmission lines is found in the construction of satellites which orbit the earth for communication of information among stations on the surface of the earth. Such satellites include antennas which point towards the earth stations so as to enable the satellite to receive and to retransmit messages from station to station.
One function of the microwave circuitry is the processing of signals received from the antennas. A particular function, by way of example, is the development of signals for the pointing of the antennas in two dimensions, namely, azimuth and elevation. To ensure a minimal weight to the microwave circuitry, and a maximum of reliability, it is advangeous to form the circuits by milling out channels in a metallic plate. Preferably, a soft, light weight metal, such as aluminum, is utilized since the softness facilitates the milling, while the light weight reduces the overall weight of the satellite. The aluminum readily conducts electricity and, accordingly, the side walls of the channels serve as side walls of coaxial lines. The inner, or center, conductors of the coaxial lines are formed of rods which are supported by insulators within the channels, the insulators serving to space the rods equidistantly from the side wall, or outer conductors, of the coaxial lines. In one advantageous embodiment of such microwave circuitry, the inner and outer conductors are both provided with a cross-sectional shape which is square.
A problem arises with respect to the coupling of the microwave energy from the antenna to the circuitry of the plate. Typically, the antenna is located at a distance from the plate and a waveguide connection is made between the antenna and the microwave circuitry of the plate. Thus, it is necessary to provide for a transition between the coaxial structure of the transmission lines within the plate and the ports of the antenna. For example, the antenna may be connected to a monopulse feed, the ports of which are connected by the waveguides to the microwave circuitry.
However, in addition to the necessary transition between the waveguide and the coaxial transmission lines of the microwave circuitry, it is also advantageous to provide for an alternative coaxial connection to the microwave circuitry at the site of the waveguide. This permits for check-out of the microwave circuitry before connection of the waveguides thereto. Thus, as may be readily visualized, it becomes desirable to place either a waveguide, extending normally from the plane of the plate at the site of transition, or a coaxial connector for the connection with a flexible cable upstanding from the plate at the site of the transition. Accordingly, the foregoing situation requires a transition which will admit for both the connection of a waveguide as well as the connection of a coaxial fitting or a flexible coaxial cable.